Many kitchen and commercial stoves now incorporate a self-cleaning feature in which the heat producing means can be activated to generate a very high temperature within the oven so as to produce substantially complete combustion of organic deposits upon the surfaces of the oven. Such temperatures frequently run as high as 380.degree. Centigrade and above.
To ensure against inadvertent opening of the oven door while the oven is at elevated temperatures, a manual latch has been employed to latch the oven door in closed position, thus requiring a physical act in addition to grasping the handle of the door. However, concerns for user safety have led to the incorporation of various additional elements for latching the door in closed position during the high temperature portion of the cleaning cycle. Some such devices have used electrical interconnections between a solenoid engagable with the latch mechanism and the circuitry controlling the high temperature phase of the appliance, particularly in the instance of electric ovens. Another approach has been the incorporation of a bimetallic strip responsive to the temperature in the oven and effective to move a pawl into a blocking position with respect to the latch subassembly, thereby preventing its movement from latched position to unlatched position when the bimetallic strip is exposed to preselected elevated temperatures. A device of this type is disclosed and described in detail in Erickson U.S. Pat. No. 3,438,666 granted Apr. 15, 1969.
To compensate for the temperature lag generally experienced between the temperature in the oven and that in the recess in which the bimetallic strip is disposed and the time lag between exposure of the bimetallic strip to the temperature and the resultant movement of the blocking pawl during the cooling portion of the cycle, Siegel U.S. Pat. No. 3,540,767 granted Nov. 17, 1970 discloses and describes a clutch assembly in the operative connection between the bimetallic strip and the blocking pawl. As the blocking pawl rotates towards blocking position, it stops at a preselected point representing less rotation than that which might be effected by the bimetallic strip during the full heating cycle and there then occurs slippage as the bimetallic strip continues to expand. When the bimetallic strip begins to cool, it immediately begins to effect movement of the blocking pawl, thus compensating for the temperature lag since the amount of relative slippage may be controlled for the temperature lag experienced in a particular oven by proper dimensioning of the parts.
However, it has been found that there nevertheless remains a problem area with respect to the time lag between the action of the bimetallic strip upon the blocking pawl and the actual temperatures within the oven. As the abument surface upon the blocking pawl approaches the point at which it would obstruct movement of the latch subassembly, movement of the latch subassembly from its latched to unlatched positions will tend to cam the blocking pawl away from a blocking position since the forces are sufficiently great to overcome the clutch.
It is an object of the present invention to provide an improved latch for ovens and the like with a high temperature latching subassembly compensating for the lag in action by the temperature sensing element as the locking position is approached.
It is also an object to provide such a latch wherein said compensating means is operative only within a narrow range of temperature and may be bypassed during operation of the latching subassembly at lower temperatures.
Another object is to provide such a latch which may be simply and readily fabricated and which is rugged and durable in operation.